Comes down to where the almanacs are downloaded from:
From the FAQ:
PSDS
HTTPS connections are made to fetch PSDS information to assist with satellite based location. These are static files and are downloaded automatically to improve location resolution speed and accuracy. No query or data is sent to these servers. These contain orbits and statuses of satellites, Earth environmental data and time adjustment information.
Qualcomm Snapdragon SoC devices also use the ntp.org NTP pool from the GNSS location service implementation when it's enabled as part of improving GNSS-based location accuracy. These connections are not used to update the system clock. GrapheneOS will likely offer more control over this in the future, although Pixels moving away from Snapdragon has moved this onto the backburner.
Qualcomm
On 4th and 5th generation Pixels (which use a Qualcomm baseband providing cellular, Wi-Fi, Bluetooth and GNSS in separate sandboxes), almanacs are downloaded from https://path1.xtracloud.net/xtra3grcej.bin https://path2.xtracloud.net/xtra3grcej.bin, https://path3.xtracloud.net/xtra3grcej.bin, https://path1.xtracloud.net/xtra3Mgrbeji.bin, https://path2.xtracloud.net/xtra3Mgrbeji.bin and https://path3.xtracloud.net/xtra3Mgrbeji.bin which currently (as of October 2022) are hosted via Amazon Web Services. We plan to offer the option to download these files from the GrapheneOS servers, but we'll retain the option to use the standard servers to blend in with other devices.
Tensor
On 6th and 7th generation Pixels (which use a Broadcom GNSS chip), almanacs are downloaded from https://broadcom.psds.grapheneos.org/lto2.dat, https://broadcom.psds.grapheneos.org/rto.dat and https://broadcom.psds.grapheneos.org/rtistatus.dat
Those are a cache for Broadcom's data available at https://gllto.glpals.com/7day/v5/latest/lto2.dat, https://gllto.glpals.com/rto/v1/latest/rto.dat and https://gllto.glpals.com/rtistatus4.dat.
Alternatively, the standard servers can be enabled in the Settings app which are https://agnss.goog/lto2.dat, https://agnss.goog/rto.dat and https://agnss.goog/rtistatus.dat providing a similar cache of Broadcom's data currently (as of October 2022) hosted on GCP (Google Cloud Platform).
Source: https://grapheneos.org/faq#default-connections
The differences are just where the data is pulled from, nothing in the data is different. You can choose to receive the data from GrapheneOS and place trust there (which makes sense given that you are trusting GrapheneOS by using it) or from Google as stock Android does.